Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$229.38	11.234%	$255.1485	$255.15	$255.15	$255.10
Purchase #2	$220.50	10.254%	$243.1101	$243.11	$243.10	$243.10
Purchase #3	$229.69	5.745%	$242.8857	$242.89	$242.90	$242.90
Purchase #4	$83.53	12.816%	$94.2352	$94.24	$94.25	$94.20
Purchase #5	$19.62	7.174%	$21.0275	$21.03	$21.05	$21.00
Purchase #6	$159.64	6.356%	$169.7867	$169.79	$169.80	$169.80
Purchase #7	$165.30	8.781%	$179.815	$179.82	$179.80	$179.80
7 purchase totals =	$1,107.66		$1,206.0087	$1,206.03	$1,206.05	$1,205.90